Very informative... thanks!

The diluted paint when spread with a brush is still shiny. I think the
trouble is in fact the paint being dried out in midair as it strikes
the surface giving it a sandpapery texture which diffuses light, spoils
the gloss. I'll try spraying with lower pressure and closer to the
work, and perhaps a top water-based urethane finish. And I will check
out that book.